-€561m (£459m, or $740m) for a single bad line of code that meant millions of people weren't offered a different browsers when they first logged on to Windows.

But the research company IDC on Tuesday handed down a far more painful finding that could cost Microsoft a great deal more if it's even close to being correct. The cost: a total of $3.3bn in direct revenues over the next four years, and about $2.3bn in profits over the same time.

That's because IDC says that Windows 8 hasn't been a hit – certainly not one that would spark a renaissance in PC buying – and there are now signs that emerging economies such as China, Africa and Latin America won't be such enthusiastic adopters of PCs as had been expected. Instead, PC sales growth there is slowing as people there turn to smartphones or tablets.